CVE-2026-105210ZITADEL 3.x before 3.4.15 and 4.x before 4.17.1 contains a missing authentication flaw in the hosted Login V1 UI, whose second-factor enrollment and initialization handlers act on an identify-only session before any primary factor is verified. Attackers knowing only a victim's login name can enroll attacker-controlled TOTP, OTP-SMS, OTP-Email, or U2F factors, overwrite the verified phone number, and enumerate users through discrepant errors.